1. Field of the Invention
The invention relates to a light module with linear LED serial group drive device, especially to the linear drive device with an intelligent control without transformers, inductors and other magnetic components.
2. Description of the Related Art
With the mature LED epitaxy and packaging technology, LED has been gradually used in the lighting field, having advantages of energy-saving, environmental protection and long life, and becoming the future mainstream of green energy sources.
The evolution of LED as a light source for illumination is beginning from general light bulbs, street lamps, to ceiling or light steel frame embedded lamps. Comparing with only one or multiple LED light bulbs, the above mentioned LED lamp is composed of dozens tandem of LEDs, so the drive circuit is different from the drive circuit of the general LED bulbs. Thus, constant current problems of the LED serial group must be considered.
With the referenced to FIG. 1, a drive circuit 10 of LED serial group comprises a bridge rectifier 33 coupled to an AC power 11, a transformer 13 having a first primary winding 131, a second primary winding 132 and a secondary winding 133, wherein the first primary winding 131 has an end coupled to the bridge rectifier 33, and another end coupled to a switch 14. The second primary winding 132 has an end coupled to the ground, and anther end produces a zero current detection signal. Further, the secondary winding 133 has a first end coupled to an LED serial group 15. A feedback circuit 16 has an input end 161 coupled to a second end of the secondary winding 133, and a second input end coupled to the first end of the secondary winding 133. A feedback signal is generated according to the input current from the second end of the secondary winding 133 and the input voltage from the first end of the secondary winding 133 to control the switch 14 in frequency way; such that the LED serial group 15 can work under constant current, and a control circuit 17 can control the power factor of the LED serial group 15. Such switching LED drive circuit is disclosed in Taiwan Utility Patent No. M435796.
The conventional switching LED drive circuit must use the magnetic components, such as: transformers or inductors. These magnetic components for driving the LED serial group 15 have an adverse impact. There is room for improvement.
Besides, the conventional LED serial group is set on a strip-type circuit board, and the traditional switching LED drive circuit will affect the arrangement of the LED on a side of the uniformity strip-type circuit board, and the Luminance uniformity.